U.S. patent number 9,371,733 [Application Number 13/885,311] was granted by the patent office on 2016-06-21 for rotor blade arrangement for a turbo machine.
This patent grant is currently assigned to MTU Aero Engines GmbH. The grantee listed for this patent is Andreas Hartung. Invention is credited to Andreas Hartung.
United States Patent |
9,371,733 |
Hartung |
June 21, 2016 |
Rotor blade arrangement for a turbo machine
Abstract
In a moving blade system for a turbomachine, in particular a gas
turbine, having at least one moving blade (1), the moving blade
system having at least one cavity (3) in which at least one tuning
mass (2) is movably situated, the tuning mass and/or the cavity
is/are adapted in such a way that the tuning mass rests against an
inner wall (3.1) of the cavity in a predefined first operating
state of the turbomachine and at least temporarily moves away from
the inner wall in a second predefined operating state of the
turbomachine.
Inventors: |
Hartung; Andreas (Munich,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hartung; Andreas |
Munich |
N/A |
DE |
|
|
Assignee: |
MTU Aero Engines GmbH (Munich,
DE)
|
Family
ID: |
45478038 |
Appl.
No.: |
13/885,311 |
Filed: |
November 5, 2011 |
PCT
Filed: |
November 05, 2011 |
PCT No.: |
PCT/DE2011/001964 |
371(c)(1),(2),(4) Date: |
June 24, 2013 |
PCT
Pub. No.: |
WO2012/065595 |
PCT
Pub. Date: |
May 24, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130280083 A1 |
Oct 24, 2013 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 16, 2010 [DE] |
|
|
10 2010 051 529 |
Feb 8, 2011 [EP] |
|
|
11153621 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D
5/12 (20130101); F01D 5/16 (20130101); Y02T
50/60 (20130101); Y10T 29/49336 (20150115); F05D
2250/241 (20130101) |
Current International
Class: |
F01D
5/12 (20060101); F01D 5/16 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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660 207 |
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Mar 1987 |
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CH |
|
19807247 |
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Sep 1999 |
|
DE |
|
10122732 |
|
Nov 2002 |
|
DE |
|
60020884 |
|
May 2006 |
|
DE |
|
60116455 |
|
Jul 2006 |
|
DE |
|
102007010378 |
|
Sep 2008 |
|
DE |
|
10 2009 010 185 |
|
Aug 2010 |
|
DE |
|
1564375 |
|
Aug 2005 |
|
EP |
|
1 892 377 |
|
Feb 2008 |
|
EP |
|
981599 |
|
May 1951 |
|
FR |
|
1024218 |
|
Mar 1953 |
|
FR |
|
1 263 677 |
|
Jun 1961 |
|
FR |
|
2 223 277 |
|
Apr 1990 |
|
GB |
|
WO 2010/094277 |
|
Jun 2011 |
|
WO |
|
Primary Examiner: Kershteyn; Igor
Attorney, Agent or Firm: Davidson, Davidson & Kappel,
LLC
Claims
What is claimed is:
1. A moving blade system for a turbomachine, comprising: at least
one moving blade; and at least one tuning mass movably situated in
at least one cavity of the moving blade system, at least one of the
tuning mass and the cavity being adapted so that the tuning mass
rests against an inner wall of the cavity in a predefined first
operating state of the turbomachine and at least temporarily moves
away from the inner wall in a second predefined operating state of
the turbomachine, wherein one of the first and second predefined
operating states is proximate to a natural frequency of the moving
blade system having a tuning mass resting against the inner wall or
positioned at a distance therefrom, wherein the proximate operating
state is between 0.9 to 0.99 times of the natural frequency of the
moving blade.
2. The moving blade system as recited in claim 1 wherein the
adaptation is of at least one of the following: a mass, shape,
surface, center of gravity or inertia tensor of the tuning mass, a
shape of the inner wall, and a surface of the inner wall.
3. The moving blade system as recited in claim 1 wherein the tuning
mass is elastically supported in the cavity, the tuning mass and
its elastic support being adapted in such a way that the tuning
mass rests against the inner wall in the first operating state and
is at least temporarily positioned a distance from the inner wall
in the second operating state.
4. The moving blade system as recited in claim 1 wherein at least
one of the tuning mass and the cavity is adapted in such a way that
the tuning mass carries out knocks against the inner wall in the
predefined operating state of the turbomachine.
5. The moving blade system as recited in claim 1 wherein the at
least one moving blade includes a plurality of moving blades and
the moving bade system includes an outer ring, the plurality of
blades, and an inner ring, and wherein the cavity is provided in or
on one of the inner ring and the outer ring.
6. The moving blade system as recited in claim 5 wherein the at
least one moving blade includes a plurality of moving blades, and
wherein the cavity is under a platform of one of the moving blades
of the moving blade system.
7. The moving blade system as recited in claim 1 wherein the at
least one moving blade includes a plurality of moving blades, each
having a corresponding vane, and wherein the cavity is provided in
one of the vanes.
8. A turbomachine comprising at least one moving blade system as
recited in claim 1.
9. A gas turbine comprising the turbomachine as recited in claim
8.
10. A method for designing the moving blade system as recited in
claim 1 wherein at least one of the at least one tuning mass and
the cavity accommodating the tuning mass is adapted in such a way
that the tuning mass rests against the inner wall in the predefined
first operating state of the turbomachine and at least temporarily
moves away from the inner wall in the second operating state.
11. A method for operating the moving blade system as recited in
claim 1 comprising: resting the tuning mass against the inner wall
in a first operating state; and at least temporarily moving the
tuning mass away from the inner wall in the second operating state.
Description
The present invention relates to a moving blade system for a
turbomachine, in particular a gas turbine which has a cavity in
which a moving mass is situated, a turbomachine and a method for
designing a moving blade system of this type.
BACKGROUND
Moving blades of turbomachines, in particular gas turbines, are
susceptible to oscillations, as a result of their elasticity and
excitation, in particular due to the working fluid flowing through
them as well as mechanical vibrations. If natural frequencies of
the moving blades are excited, the resonance may cause damage to
the turbomachine, in particular to the moving blades, and thus
reduce the service life.
U.S. Pat. No. 2,862,686 therefore proposes to provide moving
spheres inside hollow blades. Throughout the entire operation, the
centrifugal force presses the spheres in their wedge-shaped guide
radially to the outside, where they form a rib and thereby stiffen
the blade. If the blade expands as a result of heating, the spheres
subsequently slide on the inner wall of the blade cavity and thus
adapt thereto. The spheres are designed exclusively with regard to
the stiffening effect.
A blade system is known from DE 10 2009 010 185 A1 of the
applicant. Accordingly, disk-shaped damping elements, which are
freely movably situated in cavities in the blade system, carry out
frictional knocks against each other and against the inner wall and
dissipate oscillation energy from the system in this way. The
damping elements in this case are designed with regard to their
damping effect.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the oscillation
behavior of turbomachines.
The present invention provides that the natural frequencies of a
system are determined, in particular, by the system's mass or mass
distribution. If one or multiple masses is/are decoupled in a
system shortly before reaching a natural frequency of coupled
masses, or conversely, if one or multiple masses is/are added, the
natural frequency of a system which has been structurally modified
in this way changes abruptly, making it possible to traverse the
natural frequency of the original system without resonance. After
traversing this frequency, the masses which were decoupled or
coupled for the purpose of tuning the natural frequencies may be
coupled or decoupled again, and the system may be operated in an
operating state above its traversed natural frequency.
A moving blade system according to the present invention has one or
multiple detachable or non-detachable, in particular integrally
connected, moving blades. For the sake of a more concise
representation, a single moving blade is also generally referred to
in the present case as a moving blade system in the sense of the
present invention. So-called moving blade clusters, i.e., two or
more interconnected moving blades, as well as complete moving
grids, in particular so-called BLISKs (blade-integrated disks), are
referred to as a moving blade system.
The moving blade system has one or multiple cavities, which may be
designed to be open or closed. In particular, one or multiple
cavities may be provided in each vane of a moving blade or in one,
multiple or all vanes of interconnected moving blades. Additionally
or alternatively, one or multiple cavities may be provided in an
inner and/or an outer ring of a moving blade or multiple
interconnected moving blades. One or multiple cavities, which
preferably communicate with each other, are particularly
advantageously provided a least partially in and/or under the
so-called platform of one or multiple interconnected blades. In
this sense, a moving blade system in the sense of the present
invention may also include part of a rotor to which the moving
blade system is fastened and in which one or multiple of the
cavities is/are at least partially provided. The provision of one
or multiple cavities at least partially under the platform of one
or multiple blades may be advantageous, in particular with regard
to manufacturing and maintenance.
One or more tuning masses is/are movably situated in one or
multiple of the aforementioned cavities. The tuning masses may be
situated in an unbound manner, i.e., freely movable and loose, in
the particular cavity. Likewise, they may be guided in at least one
direction, preferably in the axial and/or circumferential
direction, so that they are able to move, for example, only in the
radial direction. A guide may also be provided, in particular in a
form-locked manner, for example by one or multiple, in particular
radial, channels in which tuning masses are movably guided.
Likewise, one or multiple tuning masses may also be elastically
supported in the particular cavity, for example by connecting them,
i.e., detachably or non-detachably fastening them, to the cavity
with the aid of one or multiple elastic structures, for example
leaf springs. In one preferred refinement, two or more of the
aforementioned aspects are combined, for example by additionally
elastically supporting or restraining a tuning mass, which is
guided in a form-locked manner in a radial channel, in the radial
direction with the aid of a pressure spring-like or torsion
spring-like structure.
According to the present invention, as explained above, it is
provided according to a first aspect that one or multiple of these
tuning masses, which rest against an inner wall of the particular
cavity during operation of the turbomachine as a result of the
centrifugal force, at least briefly and in particular abruptly
move(s) away from the inner wall shortly before the blade system
reaches a predefined natural frequency with the adjacent tuning
mass or adjacent tuning masses, and these tuning masses thus tune
the natural frequency of the blade system at least until they again
come to rest against the inner wall. According to a second aspect,
it is additionally or alternatively provided that one or multiple
of these tuning masses, which are positioned at a distance from the
inner wall of the particular cavity during operation of the
turbomachine, in particular due to their elastic support, at least
temporarily and, in particular, abruptly rest against the inner
wall, as a result of the centrifugal force, shortly before the
blade system reaches a predefined natural frequency with the
spaced-apart tuning mass or spaced-apart tuning masses, and the
tuning masses, in turn, thus tune the natural frequency of the
blade system, at least until they move away from the inner
wall.
For this purpose, the tuning mass(es), the cavity and/or an elastic
support of the tuning mass(es) is/are adapted in such a way that
the tuning mass rests against an inner wall of the cavity in a
predefined first operating state of the turbomachine and at least
temporarily moves away from the inner wall in a second predefined
operating state of the turbomachine. The first or second operating
state is preferably proximate to a natural frequency of the moving
blade system having a tuning mass or tuning masses which rest(s)
against the inner wall or is/are positioned at a distance
therefrom. A proximate operating state is understood to be, in
particular, an operation of the turbomachine which is in the range
of 0.9 times to 0.99 times the corresponding natural frequency.
To adapt a tuning mass according to the present invention, its
mass, its shape, its surface, in particular its coefficient of
friction and/or its surface hardness and/or surface rigidity, its
center of gravity and/or its inertia tensor, in particular, may be
suitably predefined. In one preferred embodiment, a tuning mass has
a spherical shape. The inner wall of a cavity may be adapted, in
particular, in its shape and/or surface, it being advantageous to
adapt the tuning mass and inner wall to each other with regard to
their shape and/or surface. If a tuning mass is elastically
supported or restrained in the cavity, this support or restraint is
preferably also adapted.
The adaptation of the tuning mass, inner wall and possibly elastic
support to the moving blade system, in particular to its natural
frequencies, and to the operating states of the turbomachine may
take place both numerically, in particular with the aid of
simulation, and empirically with the aid of tests. In one preferred
embodiment of a method according to the present invention,
different tuning masses are consecutively introduced into a cavity
and tested during operation of the turbomachine to see whether they
perform the desired natural frequency tuning. For this purpose, it
is advantageous, in particular, if the tuning mass(es), in one
preferred embodiment, may be nondestructively removed from a cavity
provided between rotor and platform, for example after the blade
platform has been removed from the rotor.
A tuning mass may be detached, in particular, by vibrations which
occur during operation shortly before the moving blade system
reaches a natural frequency with an adjacent tuning mass. In such a
case, the centrifugal force drives the tuning mass back against the
inner wall, which it contacts in one or multiple fully elastic or
partially plastic knocks. In one preferred embodiment, the tuning
mass and the cavity are adapted accordingly, in particular by
shaping the surface accordingly.
A moving blade according to the present invention may be used, in
particular, in a turbine (stage) or a compressor or a compressor
stage of a gas turbine, in particular in an aircraft engine. They
are preferably used in low pressure stages.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages result from the subclaims and the
exemplary embodiment. For this purpose, the single, partially
schematic drawing shows the following:
FIG. 1 shows an axial sectional view of the platform of a moving
blade having a tuning mass according to one embodiment of the
present invention.
FIG. 1 shows an axial sectional view of platform 1.1 of an only
partially illustrated moving blade 1 according to one embodiment of
the present invention. This platform is fastened to an also only
partially illustrated rotor 4 in a way which is not illustrated in
further detail. A closed cavity 3 is provided between platform 1.1
and rotor 4, i.e., on the inner ring of the moving blade which is
formed by platform 1.1. This cavity 3 is defined by the outside of
rotor 4 and the underside of platform 1.1 and may be opened by
removing blade 1 from rotor 4.
A spherical tuning mass 2 is freely movably situated in cavity 3.
The shapes of cavity 3 and tuning mass 2 are adapted to each other
in such a way that the tuning mass is pressed against radially
external inner wall 3.1 of cavity 3 by the centrifugal force during
operation of the turbomachine, i.e., while rotor 4 rotates, where
the tuning mass wanders axially at its one end (on the right in
FIG. 1) due to the wedge-shaped inner wall.
Vibrations of blade 1 occur when the rotor rotational speed
approaches a certain natural frequency of moving blade 1 with
tuning mass 2, which rests against the platform underside 3.1 of
moving blade 1 as a result of the centrifugal force, for example
the first natural bending frequency or natural torsional frequency.
The mass of tuning mass 2 is adapted or predefined or selected, in
particular, in such a way that the tuning mass abruptly, i.e.,
briefly, moves away from platform underside 3.1 of blade 1 as a
result of these vibrations before the centrifugal force drives it
back again. By moving away, the tuning mass is decoupled from blade
1 in such a way that the natural frequencies of the blades change
abruptly, this time without an adjacent or coupled tuning mass. In
this way, the natural frequency of moving blade 1 having a
contacting tuning mass 2 may be traversed without ongoing and thus
hazardous resonance occurring. It is harmless for the present
invention if resonance occurs temporarily; in the aforementioned
exemplary embodiment whenever tuning mass 2 rests again against
platform underside 3.1 after a knocking contact, since it moves
away again from there at least briefly, due to the vibrations, as a
result of its selected mass and thus, in any case, prevents
excessive buildup or instigation of the resonance. An optional leaf
spring 14 connected to the tuning mass 2 as described above is
shown schematically.
* * * * *